The design and operation of motorway diverge areas
The design and operation of motorway diverge areas
SISTM (Simulation of Strategies for Traffic on Motorways) was selected as a suitable microscopic model to further evaluate existing and alternative diverge layouts in terms of their capacity and associated operations. After a preliminary exercise and extensive initial testing of the program, four layouts (Tapper, Parallel, Taper lane drop and the Ghost Island) were modelled in order to carry out a theoretical comparison within SISTM.
The results showed that the throughput at the diverge (sum of the flow on the slip road and the mainline after the diverge) was maximised when the utilisation of the mainline lanes before the diverge was as equally used as possible. This was related to the type of layout and whether it provided the exiting driver with any lane and/or exit choice. The Ghost Island and Parallel layouts were both shown to operate well with high throughputs over a wide range of diverging percentages (0% - 60%), both providing a degree of exit choice to drivers. The Taper and Taper lane drop layout, offered no such choice, and were only suited to a smaller range of diverging percentages (0% - 30% and 30% to 50% at capacity flow levels respectively). Additional results regarding land utilisations, average speeds, lane changes and journey times/speeds provided useful information concerning the operation and potential safety of each layout.
Limitations to the SISTM model were identified with possible enhancements suggested. In addition, measures to improve the capacity and/or the lane distribution near the diverge were examined, such as installing a hard shoulder running lane, real time road markings and the use of variable speed limits.
Conclusions included a design process flowchart containing a toolkit of measures to improve the operation and capacity of the diverge. Recommendations included making the Ghost Island diverge layout (with or without a lane drop) a standard design layout with its ability to reduce swooping and potentially improve throughput. In addition, field trials should be carried out to assess measures such as real time markings in their effectiveness in trying to optimise the lane distribution on the mainline before the diverge.
University of Southampton
Wall, Graham
1f68f5b7-d1a9-4daf-9440-e7cf49f33606
2004
Wall, Graham
1f68f5b7-d1a9-4daf-9440-e7cf49f33606
Wall, Graham
(2004)
The design and operation of motorway diverge areas.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
SISTM (Simulation of Strategies for Traffic on Motorways) was selected as a suitable microscopic model to further evaluate existing and alternative diverge layouts in terms of their capacity and associated operations. After a preliminary exercise and extensive initial testing of the program, four layouts (Tapper, Parallel, Taper lane drop and the Ghost Island) were modelled in order to carry out a theoretical comparison within SISTM.
The results showed that the throughput at the diverge (sum of the flow on the slip road and the mainline after the diverge) was maximised when the utilisation of the mainline lanes before the diverge was as equally used as possible. This was related to the type of layout and whether it provided the exiting driver with any lane and/or exit choice. The Ghost Island and Parallel layouts were both shown to operate well with high throughputs over a wide range of diverging percentages (0% - 60%), both providing a degree of exit choice to drivers. The Taper and Taper lane drop layout, offered no such choice, and were only suited to a smaller range of diverging percentages (0% - 30% and 30% to 50% at capacity flow levels respectively). Additional results regarding land utilisations, average speeds, lane changes and journey times/speeds provided useful information concerning the operation and potential safety of each layout.
Limitations to the SISTM model were identified with possible enhancements suggested. In addition, measures to improve the capacity and/or the lane distribution near the diverge were examined, such as installing a hard shoulder running lane, real time road markings and the use of variable speed limits.
Conclusions included a design process flowchart containing a toolkit of measures to improve the operation and capacity of the diverge. Recommendations included making the Ghost Island diverge layout (with or without a lane drop) a standard design layout with its ability to reduce swooping and potentially improve throughput. In addition, field trials should be carried out to assess measures such as real time markings in their effectiveness in trying to optimise the lane distribution on the mainline before the diverge.
Text
947077.pdf
- Version of Record
More information
Published date: 2004
Identifiers
Local EPrints ID: 465369
URI: http://eprints.soton.ac.uk/id/eprint/465369
PURE UUID: c55e2640-54c3-4c04-b1af-8ec444796db9
Catalogue record
Date deposited: 05 Jul 2022 00:40
Last modified: 16 Mar 2024 20:08
Export record
Contributors
Author:
Graham Wall
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics